In 1996, more than 75 million people worldwide used cellular telephones. Reliable predictions indicate that there will be over 300 million cellular telephone customers by the year 2000. Within the United States, cellular service is offered not only by dedicated cellular service providers, but also by the regional Bell companies, such as U.S. West, Bell Atlantic and Southwestern Bell, and the national long distance companies, such as AT&T and Sprint. The enhanced competition has driven the price of cellular service down to the point where it is affordable to a large segment of the population.
Wireless subscribers use a wide variety of wireless devices, including cellular phones, personal communication services (PCS) devices, and wireless modem-equipped personal computer (PCs), among others. The large number of subscribers and the many applications for wireless communications have increased wireless traffic to the point that communication channels are frequently unavailable when a subscriber attempts to initiate a call in a wireless communication system.
When a subscriber is unable to access a channel when the subscriber initiates a call, the wireless system may "reserve" the next available channel for the missed call and then initiate a return call to the subscriber's device when the channel is finally available. In such a system, the wireless system may also assign a priority level to each missed call in order to service higher priority calls first. For example, 911 calls (emergency calls) may be assigned the highest priority and premium subscribers who pay a higher service fee may be assigned a higher priority level than regular subscribers who pay the standard service fee. Calls having a higher priority level are served before lower priority level calls when the next channel comes available. As between two calls having the same priority level, the calls are served in the order received (i.e., chronological) when the next channel comes available. However, if a subscriber moves from one base station coverage area to another, there is no way to maintain the original priority level of that subscriber's missed call with respect to the pending missed calls in the new coverage area.
There is therefore a need in the art for a wireless communication system that is able to maintain the proper priority level of a missed call in a new coverage area when a subscriber moves from a first coverage area in which the call was missed to a new coverage area. In particular, there is a need in the art for an improved wireless communication system that tracks the priority levels of all missed calls in a plurality of base station coverage areas and which maintains priority levels of missed calls on a system-wide basis, rather than within individual base station coverage areas.